Wireless local area networks (WLANs) media access control (MAC) protocols perform carrier sensing to avoid collisions. The MAC protocol employs carrier sense multiple access with collision avoidance (CSMA/CA) that avoids collisions by transmitting only when the channel is determined to be idle. CSMA is a probabilistic MAC protocol in which a node verifies the absence of other traffic before transmitting messages on the shared transmission medium. By avoiding collisions, CSMA/CA improves the performance. In CSMA/CA, when a channel is sensed busy before transmission, the transmission is deferred for a random interval. This reduces the probability of collisions in the channel.
Dense deployment of WLANs is becoming more common. Dense environments contain large numbers of access points located in a given area. In a dense environment, there is a high chance that some stations are located very close to their associated access point, which results in a low path loss, and therefore high quality of the link.